The recombination system which catalyzes the integration of bacteriophage Mu is most unusual, since it recognizes specific attachment sites on the phage chromosome and recombines them with an apparently random sequence on the host chromosome. The goal of this research program is to elucidate the mechanism by which this integration occurs. We will continue our studies by 1) genetic and physical analysis of effects of integration deficient mutations on integration, DNA synthesis, and phage development, 2) further analysis of host deletion mutations induced by Mu, and 3) completion of the correlation of the genetic and physical maps of Mu with particular emphasis on the middle of the Mu genome. BIBLIOGRAPHIC REFERENCES: Moore, D.D., J.W. Schumm, M.M. Howe, and F.R. Blattner (1977) Insertion of Mu DNA into phage lambda in vitro. DNA Insertions. Cold springs Harbor Press. Howe, M.M., M. Schnos, and R.B. Inman (1977) DNA partial denaturation mapping studies of packaging of bacteriophage Mu DNA. DNA Insertions. Cold Spring Harbor Press.